Those on wheelchairs have some difficulty in boarding and alighting from public transport vehicles such as, for example, buses, trams and trains, as such public transport vehicles often have a gap that has to be crossed on boarding or alighting. For busses and trams, one solution is to fit low floor buses with a powered ramp that can be lowered onto the curb at an entry/exit door to form a negotiable bridge to allow the wheelchair to roll from the curb onto the bus or from the bus onto the curb. However, it is expensive to fit each bus and tram with such a powered ramp. Their use significantly increases the time taken for boarding and alighting. Another solution is to have a suspension system on the curb side of the bus or tram that enables the curb side to be lowered. This still leaves a gap for wheelchairs and is mainly used for elderly passengers.
A final solution was to have wheel chairs with continuous tracks that can cross gaps. Such wheelchairs are specifically built, are bulky and expensive, and have not met with success.